In the determination of the appropriate dose for the individual patient lie both the difficulty and the danger of tuberculin therapy. A dose in excess of the exact amount required frequently proves disastrous and has even hastened death. The possibilities of giving the wrong dose are increased by the very wide limits of tuberculin dosage, one patient requiring a dose one thousand or one million times that required by another patient, who is sometimes apparently of the same type.
There is no way of determining accurately the proper dose for a patient who has never taken tuberculin. The initial dose is always a matter of guess. Experience and judgment may indeed help one to guess more correctly, but they do not insure accuracy. White and Williams estimate the initial dose from the size of the areola produced by a von Pirquet test made with a definite amount of tuberculin; but